Merge branch 'refs/heads/master_gh'

# Conflicts:
#	pyproject.toml

src/betterproto/__init__.py

@@ -749,7 +749,7 @@ class Message(ABC):
                 group_current.setdefault(meta.group)
 
             value = self.__raw_get(field_name)
-            if value != PLACEHOLDER and not (meta.optional and value is None):
+            if value is not PLACEHOLDER and not (meta.optional and value is None):
                 # Found a non-sentinel value
                 all_sentinel = False